1. Field of the Invention
This invention relates to a surgical head clamp, and more particularly, to a surgical head clamp wherein the means for axially adjusting, rotating and locking the head engaging pins are all on the same side of the clamp.
2. The Problem in the Art
Hickmann U.S. Pat. No. 4,169,478, issued Oct. 2, 1979, shows a surgical head clamp having a C-shaped frame. A first head engaging pin is mounted in a pin holder threaded into one side of the frame. Two other head engaging pins are mounted on the ends of a rotatable bracket, or clevis, on the opposite side of the frame. An adjustment knob is connected to the rear (outer end) of the pin holder. Turning the knob translates the first pin axially, thereby adjusting the distance between the first and the other opposed pins to facilitate clamping a patient's head at the three points defined by the pin points. The clevis holding the second and third pins is selectively rotatable about an axis of rotation which is coaxial with the longitudinal axis of the first pin. Selective rotation of the clevis about this axis permits the surgeon to adjust the angular relationship between the frame and the patient's head. The clevis also rotates about a transverse axis, so that the pins on the clevis can accommodate varying geometries of the head.
The Hickmann design has been found to present certain limitations in use: First, the bulkiness of the end of the clamp having the single pin and adjusting screw may hamper the surgeon's preferred hand positions or may tend to limit his access to a head location adjacent the knob.
Second, adjusting the position of the single pin to secure the patient's head in the clamp, should, ideally, result in equal clamping forces being applied by all pins. However, a skull is not a rigid body and will experience different deformations; and there will be variations from patient to patient depending on the location of the applied forces. Therefore, as the single pin is tightened and it applies a force against the patient's head, the distribution of the reactive forces by the opposite two pins is somewhat unpredictable and may be unequal; and therefore, one of opposing two pins may seat with substantially less force than the other one.